Moistening system for rotary offset machine



1959 N w. TRISLER 9 5 MOISTENING SYSTEM FOR ROTARY OFFSET MACHINE FiledMay 2, 195a Anwmw: Maison WV. Frasier Witness )3 m M dHorn y UnitedStates Patent MOISTENING SYSTEM FOR ROTARY OFFSET MACHINE Nelson W.Trisler, Des Moines, Iowa Application May 2, 1956, Serial No. 582,122

6 Claims. (Cl.-101-136) This invention is a novel plate moisteningsystem for offset printing presses and one that is particularly usefulin multicolor, single impression work. It features a fountain roller inthe moistening system the surface of which is rotated so as to have amoistened surface portion brought by the shortest route to a position tobe contacted by the ductor roller. The ductor roller is arranged inrelation to the fountain so that the surface of the roller therein hasmoved only a limited number of degrees of rotation from the fountainliquid when the ductor roller contacts the fountain roller. Thiscooperation between the ductor and fountain rollers provides extremelyconsistent and uniform moistening of the plate surface with resultingexcellent printing and with less attention required of the operator.Once the proper balance between ink and moisture has been establishedfor the particular printing problem involved, the system will operatefor long periods without getting out of adjustment.

This application claims in part structure shown but not claimed in mycopending application Ser, No. 551,559, filed December 7, 1955.

In use on multi-color presses of the single impression type, themoistening system also features a reverse order of application of inkand moisture to all plates after the first one to contact the blanketafter an impression is made. By reversing the order in which ink andmoisture are applied, etching is minimized on plates after the firstone. Additional plates after the first one are insulated from etching bya film of moisture laid onto the plate just before it contacts theblanket. In this manner, wearing or etching of the additional plates byink on the blanket from the first plate is minimized. As it is as aresult of such etching that inks are carried from one systemintoanother, minimizing this etching minimizes color distortion or tinting.It has also been found that plates used on presses incorporating mynovel moistening system makes it possible to print up to twenty-fivepercent more images before the plate is worn out than is true whenconventional ratchet drive roller moistening systems are used.

Accordingly it is the principal object of this invention to-provide anovel moistening system; one that:

(1) provides uniform moistening of a plate surface.

(2) provides consistent moistening of plates during a printing run.

(3) increases plate life.

(4) requires less skill of the operator to get satisfactory results inprinting.

(5) minimizes color distortion when multi-color single impressionprinting is done.

While the foregoing specifically listed objects are the main ones ofthis invention, it is my intention to include as objects hereof any suchas may be clear to a skilled, offset printing press operator-mechanicafter he has read this specification, including the claims, and examinedthe accompanying drawings which. are briefly described as follows:

Fig. l is a diagrammatic view of a multi-color, single impression,offset printing press incorporating my novel moistening system;

Fig. 2 is a fragmentary, perspective, diagrammatic view of my novelmoistening system; and

Fig. 3 is a fragmentary, diagrammatic view of an offset press equippedwith a modified form of my novel moistening system.

Referring to the drawings there is shown in Fig. 1 a multicolor, singleimpress, offset printing press having the usual impression or platencylinder 10 which cooperates with blanket cylinder 12 in applyingprinted impressions to paper 14 which is fed between the cylinders byconventional mechanism which, therefore, is not shown. Blanket cylinder12 is provided with the usual blanket 16 which carries the impressionfrom the inked plates on the first plate cylinder 18 and the secondplate cylinder 20. Cylinder 18 is called the first plate cylinder,because it is the first of the plate cylinders to contact the blanket 16after it has transferred its impression to a sheet of the paper 14.Another way of stating this is that plate cylinder 18 is the first toapply fresh ink to the blanket in each printing cycle. An ink fountain22, ink fountain roller 24, ink ductor roller 26, ink transfer andspreading rollers 28 and form rollers 30 provide ink for the platecylinder 18. This same plate cylinder has a moistening system associatedwith it which system comprises a fountain 32 containing liquid 33,fountain roller 34, ductor roller 36, hard surface transfer roller 38and molleton or cloth covered roller 46. An appropriate structure isprovided to drive the fountain roller such as ratchet mechanism 41. Acontrol 43 determines the amount of rotation that the ratchet is allowedto impart. Ratchet system 41 and control 43 are of the type described inUnited States Patent No. 2,065,535 (The elements 111l25). Thismoistening system is unconventional in that the fountain roller 34 isrotated by appropriate ratchet mechanism in the direction shown by thearrow in it. With the exception of the direction of rotation, theratchet drive is conventional. The surface of fountain roller 34 movesup, by the shortest route, out of liquid 33 to a position to becontacted by the ductor roller 36. Ductor roller 36 is conventional andis moved back and forth as shown by the double headed arrow on pivotedarms, as suggested by the element 42, to take moisture from the fountainroller 34 and carry it to transfer roller 38. These arms and the ductorroller are preferably constructed and arranged to barely clear thefountain 32 so that ductor roller 36 contacts the surface of thefountain roller 34 as near to the surface of liquid 33 as possible andcertainly within ninety degrees of rotation of the surface of thefountain roller from the surface of the liquid 33 in the fountain. Thiscombination of relative location of the ductor roller and fountainroller and the direction in which the latter rotates is one thatprovides both consistent moistening of plates during a printing run anduniform moistening over the face of the plate for each impression. Theconsistency and uniformity of the moistening achieved with this systemillustrated in Fig. 2 where it can be seen that a film of moisture,represented by the stipling at 35, extends entirely along the length ofthe ratchet driven fountain roller 34. If this film is contacted soonafter the fountain roller emerges from the liquid in the fountain, itremains evenly spread on the roller. Surface tension will not yet haveseparated the liquid into patches on the surface of the [fountainroller. When fountain roller 34 is contacted by ductor roller 36, thelatter is evenly moistened along its entire length and to the extentdetermined by the setting of the ratchet drive of the fountain roller.As the degrees of rotation of the. fountain roller surface after itemerges from the liquid before it is contacted by the ductor increases,the efiiciency of the moistening system decreases rapidly. The longerthe delay at this point in the operation, the greater is the likelihoodthat surface tension will separate the liquid film into patches. Whenthe liquid is not evenly distributed, the plates are less uniformlymoistened which results in ink being carried back into the moisteningsystem. As the ink used is greasey in nature, it will accentuate thesurface tension problem when it is carried back into the moisteningsystem. Surface tension operates more readily on a greasey surface thanon one that is free from grease. Conversely, when moistening is uniformand consistent, little or no ink is carried back. Conditions favorableto uniform moistening are maintained for extended periods. As the ductorroller 36 contacts the rapidly rotating transfer roller 33, moisture istransferred evenly along the transfer roller at several locations.Similarly, moisture is evenly placed on the molleton roller 40 when itrotates in contact with the transfer roller 38.

When the plates are well moistened, which includes both consistency anduniformity, there are several advantages that follow. As pointed outabove continued even moistening for extended periods is one. Another isthat ink sticks to the plates only where intended which in turn has twoimportant results. In sticking only to the image formed on the plate,ink is available to be transferred in the pattern intended only. Clearimpressions are made therefore. When the plate is not supplied with adeuate quantities of ink on its pattern, it wears more rapidly than itwill otherwise. It can be seen that all these advantages are intertwinedand correlated and that once a consistent and uniform moistening isaccomplished, the other results follow. It seems also that it is easierto establish a proper balance between ink and moisture when my novelmoistening system is used than when conventional ratchet driven, rollerapplied moistening is employed.

Plate 20 is provided with an inking system generally designated 44 likethe one for plate 13 the parts of which are numbered in detail. There isone difference between these two inking systems. They apply ink inrelation to the application of moisture in reverse order to each other.The system for plate 18 is conventional in respect to the order ofapplication, but the order for plate 20 is reversed. It can be seen fromthe arrows on cylinder 18 that as a portion of the plate on the cylinderleaves the blanket 16, it will first have moisture applied to it andthen be provided with ink. This is the conventional arrangement. In mysystem as shown in Fig. 1 for the second plate 20, ink is first appliedby inking system 44 and then the plate encounters the rollers of themoistening system 46 which, except for this positioning, is like the one32- 50 for plate is. A ratchet system 47 and control structure 4') areprovided for moisture system 46. These units also are of the typedescribed in United States Patent 2,065,535. The prior art has taughtintroducing moisture with the ink, but to my knowledge I am the first toapply the moisture specifically after the ink as the last step inpreparing the plate for contact with the blanket. This statement is alsolimited to the application of moisture in actual printing which mightproperly be assumed from the words preparing the plate for contact withthe blanket. Even the systems in which the moisture is introduced intothe ink and onto the plate with the do so far back in the inking system.

As a result of my order of applying ink and moisture, the plate has beenfreshly moistened just before the second plate Ztl contacts the blanket.No roller engages the second plate after moisture has been applied andbefore contact between the plate and the blanket. In short moisture isapplied between the application of ink and the contact of the plate andblanket. It is believed that it is for this reason that there is aninsulating moisture film on the plate so that there is little, or nomechanical etching of the plate 20 with the image of plate 18 that hasbeen transferred previously to the blanket. There is further evidencesupporting the belief that the film of moisture applied as the last stepin preparing plates after the first one for contact with the blanket isbeneficial in preventing etching and plate wear. When about seventy-fivepercent of the total moisture needed in a given situation is added withmoisture system 46 in Fig. 1 and only twenty-five percent is added withsystem 3240, less etching and plate'wear occurs than when the moistureadded by the two systems is more evenly divided between them orunbalanced in the opposite direction.

If a conventional order of application is used for successive platesafter the first one in single impression, multi-color printing as shownhere; there is a very noticeable tendency for the image from plate 18,the first plate, to be transferred from the first plate to the blanketand then to the successive plates. If the wear between the successiveplates after the first one and the blanket is not minimized, the secondplate will become etched mechanically to carry also the image of thefirst plate. When the second plate becomes etched With the first plateimage as well as its own, both images will take ink from inking system44. Via the blanket the inks from the two inking systems will becomemixed which could be called tinting in relation to the lighter color anddilution for the darker color. When overlay work, printing one colordirectly on top of another, is done; my novel order in applying inkfirst and then moisture is particularly advantageous. Most of the colordistortion that occurs when a conventional system is used is from thefirst system into successive systems, because much of the ink on theblanket is removed as an impression is made. However, there will be somedistortion, either diluting or tinting, from successive inking systemsback into the first one also. When my order of ink and moistureapplication is used for plates after the first one, color distortion isnot totally eliminated, but it is reduced to the point that verysatisfactory printing for long runs can be accomplished.

Fig. 3 shows a modified form of the moistening system for the plates. Inthat figure, the blanket 48 on the blanket cylinder 50 (shown only infragment) contacts the plate on plate cylinder 52 in the usual manner.An inking system 54 like those shown in Fig. 1 provides ink and themoisture system 56 provides moisture as the last step again as inFig. 1. The first cylinder is not shown. This moisture system differsfrom the system 46 in that the molleton roller 58 does not contact theplate but instead engages a transfer roller 60 which is the same type ofroller as the form rollers of the inking system 44 or 54. This rollerwill take ink from plate cylinder 52 if the quantities of ink on it areexcessive and add ink to the cylinder, or more accurately the plate onthe cylinder, if the inking system 54 is not applying adequatequantities. For this reason this form of the invention will remain inbalance without attention very well. As the ink and moisture will notreadily mix, this same roller 60 also serves to transfer moisture to theplate on cylinder 52 as the last step before the plate contacts theblanket 48.

When my improved moistening system is used, the ranges of adjustment onmoisture and ink quantities can be substantially greater and stillobtain satisfactory results than is true with conventional ratchetdriven moisture systems. That is to say much less moisture than inconventional machines will be adequate and more moisture and ink can beused without interfering with the printing of clear copy. Obviouslypersons only slightly skilled in gaging how to adjust the moisture andink quantity controls for proper printing will be more apt to besuccessful with a press equipped with my moisture system than they wouldbe with a conventional ratchet controlled, roller fed moisture system.

The reverse rotation of the fountain roller in the moistening system wasfirst used by me rather accidentally in connection with making a systemsimilar to that shown in Fig. 3. The linkage used to drive the fountainroller ratchet was connected without much thought as to the directionwhich the fountain roller would turn. As the device was used, however,it was noticed that the control of the balance between ink and moisturewas particularly good. This was at first attributed entirely to movingthe molleton roller back off the plate and into a position to becontacted by the ductor roller. It was anticipated that there would beperhaps a little more ink than usual picked up by the molleton andductor rollers. It was expected that they would have to be cleaned alittle more often than usualafter a run of fifty thousand impressionssay. As a matter of fact, however, the cloth covered rollers (the ductorroller is also cloth covered) were operated extensively with noindication that they were sufficiently ink laden to require Washing. Infact more than three million impressions have been run with some ofthese rollers without cleaning them. It was then that I gave moreattention to all of the details of the way the system was operating. Itwas soon determined that one of the most advantageous things in mystructure for moistening was the direction of rotation of the fountainroller in relation to the position of the ductor roller.

I have disclosed my invention by describing it and showing with drawingspractical embodiments thereto, and I now particularly point out anddistinctly claim these structures and combinations of structures that Ibeblieve to be my invention.

I claim:

1. In a multi-color, single impression offset printing press having ablanket cylinder, an impression cylinder cooperating therewith, firstand second plate cylinders cooperating with said blanket cylinder, firstand second inking systems each comprising, at least an ink fountain,ductor roller, transfer rollers and a form roll for depositing ink on aplate on said plate cylinders; and first and second moistening systemseach comprising at least a fountain, a fountain roller, a ductor roller,a transfer roller, and a roller cooperating with the transfer roller anda plate on one of said plate cylinders; the improvement comprisinghaving said second moistening system apply moisture to a plate on saidsecond plate cylinder after the plate is inked and before it depositsink on a blanket on said blanket cylinder in a normal printing cycle;and said first moisture system applies moisture to a plate on said firstplate cylinder before the plate is inked and after it has deposited inkon said blanket cylinder in a normal cycle of printing.

2. The multi-color, single impression, offset printing press of claim 1in which there is a separate means secured to each said first and secondmoistening systems for controlling the amount of moisture applied byeach of said first and second moistening systems.

3. The multi-color, single impression, offset printing press of claim 2in which the fountain roller in each of said first and second moisteningsystems rotates as to bring its surface by the shortest route from thesurface of liquid in its fountain to a position to be contacted by itsductor roller.

4. The multi-color, single impression, offset printing press of claim 1in which the fountain roller in each of said first and second moisteningsystem rotates as to bring its surface by the shortest route from thesurface of liquid in its fountain to a position to be contacted by itsductor roller.

5. The multi-color, single impression, offset printing press of claim 1in which a transfer roller in said second moistening system is amolleton roller that contacts said ductor roller and a roller thatcooperates with a plate on said second plate cylinder; said molletonroller remaining out of contact with said second plate cylinder.

6. The multi-color, single impression, offset printing press of claim 1in which the fountain roller in each of said first and second moisteningsystems rotates as to bring its surface by the shortest route from thesurface of liquid in its fountain to a position to be contacted by itsductor roller; and a transfer roller in said second moistening system is:a molleton roller that contacts said second moistening system ductorroller and a roller that cooperates with a plate on said second platecylinder; said molleton roller remaining out of contact with a plate onsaid second plate cylinder.

References Cited in the file of this patent UNITED STATES PATENTS2,054,830 Osborne Sept. 22, 1936 2,065,535 Morse Dec. 29, 1936 FOREIGNPATENTS 822,735 France Jan. 6, 1938

